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Compositions of near-solidus peridotite melts from experiments and thermodynamic calculations

Baker, M. B. and Hirschmann, M. M. and Ghiorso, M. S. and Stolper, E. M. (1995) Compositions of near-solidus peridotite melts from experiments and thermodynamic calculations. Nature, 375 (6529). pp. 308-311. ISSN 0028-0836. http://resolver.caltech.edu/CaltechAUTHORS:20120820-135824877

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Abstract

Mid-ocean-ridge basalts (MORBs) are probably a mixture of liquids formed by near-fractional melting of upwelling mantle over a range of pressures. Thus, an understanding of MORB genesis requires knowledge of the compositions of near-solidus melts of mantle peridotite, which have not been measured experimentally. Here we present the results of melting experiments on peridotite using a two-stage diamond-aggregate extraction technique, and the results of thermodynamic calculations of peridotite melting. Both the experiments and the calculations show that at 10 kbar, near-solidus melts (melt fraction F = 0.02-0.05) of fertile peridotite are enriched in SiO_2, A1_(2)O_3 and Na_(2)O and depleted in FeO* (all iron as FeO), MgO and CaO relative to higher-degree melts. At F≈0.02, the partial melt has ~57 wt% SiO_2 and is qualitatively similar to silica-rich melt inclusions found in spinel peridotites worldwide. At low melt fractions (F≤0.08), measured and calculated clinopv roxene/ liquid (cpx/liq) partition coefficients for TiO_2 are larger than those calculated from cpx-liq pairs in higher-melt-fraction experiments. This change in titanium partitioning just above the fertile peridotite solidus implies that other highly charged elements (such as Hf, Zr, Th and U) exhibit similarly complex behaviour during the initial stages of mantle melting.


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http://dx.doi.org/10.1038/375308a0DOIUNSPECIFIED
http://www.nature.com/nature/journal/v375/n6529/abs/375308a0.htmlPublisherUNSPECIFIED
Additional Information:© 1995 Nature Publishing Group. Received 18 October 1994; accepted 4 April 1995. We thank E. Klein for helpful comments. This work was supported by the US NSF.
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Record Number:CaltechAUTHORS:20120820-135824877
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20120820-135824877
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ID Code:33365
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:21 Aug 2012 17:45
Last Modified:21 Aug 2012 17:45

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